The above just led me to think up a whole can of worms....
First, I was thinking that the "heavy bombardment" missiles that could be handed off to a FAC for terminal guidance would be a good thing - it would add to the complexity of trade-offs in weapons-mix decisions.
Second, I was thinking that it would also be a good thing by allowing a planetary base to take its entire system under fire by long-range drones (assuming it had FAC GB based on it).
Third, I just realized that the "hand off" ability might be necessary if you introduce drones. Otherwise you've just given a huge range advantage to ships over planets - the ships can standoff outside of the planet's missile range and pound it into dust with drones. This seems to contradict your original goal of having "bastion planets" which would be difficult to attack from space.
The hand-off idea is interesting and would reflect real life, although I think ships need specialised equipment to handle it. It could get a little messy in the interface though. I will probably look at this when I finally get around to my EW overhaul.
With regard to bombarding planets from long range. It is possible but the requirements to achieve it successfully are considerable. Firstly, if you assume size 16+ drones, then each launcher is going to require a lot of space. A cruiser with a dozen size 4 launchers would only mount 3 drone launchers and the rate of fire would be reduced by 75%. A defender would have to deal with 25% of the missiles in each salvo and just 6.25% of the total weight of fire over time. Secondly, you are probably firing blind without any real idea of the defenders. NPRs in v4.8 are aware of drones so they will be taking steps to defend their important planets against drone attack. You could expend a lot of time and effort setting up an attack with a small number of drones when a heavier weight of fire from closer in might be a lot more effective. Finally, a ship designed purely to fire drones is going to be very vulnerable when facing a regular warship. I have just starting building drones in my own campaign and then only design to use them so far has a single launcher for recon drones. Its a 10,000 ton CA with six size 4 launchers and a size 16 launcher for the drones. It carries 90 missiles and just 6 drones. Those 6 drones take up 21% of the magazine space. I will obviously listen to feedback on how they fare but with the drone engine at 0.25 HS, or 5 MSP, the sheer size of drones makes them difficult to use effectively as a weapon.
Steve
